This invention relates to light-emitting or receiving devices (or parts) such as LED, laser diodes, and photo-sensors, and more particularly, to light-emitting or receiving devices having improved weatherability, chemical resistance, hardness, moisture or water resistance, and optical properties.
The prior art light-emitting or receiving devices such as LED, laser diodes, and photo-sensors have been manufactured through encapsulation of light-emitting diodes and similar elements by casting epoxy resin followed by polymerization.
The light-emitting or receiving devices encapsulated with epoxy resin, however, have the following drawbacks.
(1) Since the epoxy resin has poor weatherability, its outdoor use is substantially limited. This is because light-emitting elements experience a drastic drop in luminous power with a lapse of time and light-receiving elements experience a drop in light-receiving sensitivity with a lapse of time when used outdoors.
(2) Since it takes a long time of 5 to 20 hours to cure the epoxy resin, the productivity of light-emitting or receiving devices is low.
(3) Since the epoxy resin has poor mold release characteristics after its cast-polymerization, the productivity of light-emitting or receiving devices is low.
If a mold release agent is used to improve mold release, it would be necessary to remove the mold release agent adhered to the surface of the epoxy resin encapsulant, resulting in a complicated production process.